This invention relates in general to flames for vehicles and in particular to an improved structure for a joint between a side rail and a cross member in a vehicle frame.
A vehicle, such as an automobile or light track, includes among its major structural components a body, an engine, a drive train, and a suspension system. The vehicle further includes a vehicle frame which serves as a platform for the other components. The body and engine are stacked on top of the vehicle frame, and the drive train and suspension system are hung underneath it.
The vehicle frame typically includes two elongated and parallel side rails having a plurality of cross members extending therebetween to connect them together. The cross members extend generally perpendicular to the side rails and parallel with one another. The connections between the side rails and the cross members of the vehicle frame are known as joints.
A vehicle frame should be strong to support the vehicular components and to maintain its structure in case of a collision. It is also desirable for a vehicle frame to possess a high degree of torsional stiffness or rigidity. The stiffer the frame, the easier it is for a vehicle manufacturer to fine tune the suspension system. A finely tuned suspension system results in significant ride and handling improvements for the vehicle.
In the past, the side rails of a vehicle frame were typically formed having an I-shaped or an open C-shaped cross section. An open C-shaped cross section side rail is defined by a vertically extending side portion and upper and lower horizontally extending flange portions. Side rails of a vehicle frame have also been formed having a closed C-shaped cross section. A closed C-shaped cross section is defined by a vertically extending side portion, upper and lower horizontally extending flange portions, and upper and lower vertically extending lip portions at the ends of the flange portions. It has been found that forming the side rails with a closed C-shaped cross section will increase the torsional stiffness of the side rails. In view of the increased torsional stiffness, it would be desirable to provide a vehicle frame including side rails with a closed C-shaped cross section.
Unfortunately, a closed C-shaped cross section creates difficulties in connecting a cross member to the side rail. When the side rail has an I-shaped or an open C-shaped cross section, a cross member can lie between and adjacent to both the upper and lower horizontally extending flange portions of the side rail. This allows the cross member to be connected to both flange portions to form a stronger and stiffer joint. However, when the side rail has a closed C-shaped cross section, the upper and lower vertically extending lip portions prevent the cross member from lying adjacent to the flange portions. As a result, the cross member cannot be directly connected to the flange portions.
One alternative is to connect the cross member to the vertically extending side portion, instead of the horizontally extending flange portions. However, such a connection weakens and reduces the stiffness of the joint. Another alternative is to form opposing notches in the upper and lower vertically extending lip portions so that the cross member can be positioned therein. This allows the cross member to lie adjacent to the horizontally extending flange portions for connection thereto. However, forming notches in the lip portions also weakens and reduces the stiffness of the joint. Thus, it would be desirable to provide a structure for a vehicle frame joint which includes a side rail having a closed C-shaped cross section and which also forms a strong, stiff joint and vehicle frame.